Abstract
Abstract. Produced by the incomplete combustion of fossil fuel and biomass, black carbon (BC) contributes to Arctic warming by reducing snow albedo and thus triggering a snow-albedo feedback leading to increased snowmelt. Therefore, it is of high importance to assess past BC emissions to better understand and constrain their role. However, only a few long-term BC records are available from the Arctic, mainly originating from Greenland ice cores. Here, we present the first long-term and high-resolution refractory black carbon (rBC) record from Svalbard, derived from the analysis of two ice cores drilled at the Lomonosovfonna ice field in 2009 (LF-09) and 2011 (LF-11) and covering 800 years of atmospheric emissions. Our results show that rBC concentrations strongly increased from 1860 on due to anthropogenic emissions and reached two maxima, at the end of the 19th century and in the middle of the 20th century. No increase in rBC concentrations during the last decades was observed, which is corroborated by atmospheric measurements elsewhere in the Arctic but contradicts a previous study from another ice core from Svalbard. While melting may affect BC concentrations during periods of high temperatures, rBC concentrations remain well preserved prior to the 20th century due to lower temperatures inducing little melt. Therefore, the preindustrial rBC record (before 1800), along with ammonium (NH4+), formate (HCOO−) and specific organic markers (vanillic acid, VA, and p-hydroxybenzoic acid, p-HBA), was used as a proxy for biomass burning. Despite numerous single events, no long-term trend was observed over the time period 1222–1800 for rBC and NH4+. In contrast, formate, VA, and p-HBA experience multi-decadal peaks reflecting periods of enhanced biomass burning. Most of the background variations and single peak events are corroborated by other ice core records from Greenland and Siberia. We suggest that the paleofire record from the LF ice core primarily reflects biomass burning episodes from northern Eurasia, induced by decadal-scale climatic variations.
Highlights
In the last decades, the Arctic region has experienced the strongest surface air temperature increases globally, referred to as the Arctic amplification (Serreze and Barry, 2011), leading to a range of severe consequences for glaciers, sea ice, wildlife, and local human societies and partially explained by strong snow and sea ice feedbacks implying surface albedo changes
We present the long-term and high-resolution Refractory black carbon (rBC) record from Svalbard derived from the combination of the Lomonosovfonna 2009 (LF-09) and LF-11 ice cores spanning the time periods 1222– 2004 and 2004–2011, respectively (Fig. 2a)
In the LF-09 ice core, rBC concentrations are generally low with a range between the limit of detection (LOD) (i.e., 0.051 ng g−1) up to 39.0 ng g−1 in 1980, an average of 1.2 ± 2.3 ng g−1 and a median of 0.6 ng g−1
Summary
The Arctic region has experienced the strongest surface air temperature increases globally, referred to as the Arctic amplification (Serreze and Barry, 2011), leading to a range of severe consequences for glaciers, sea ice, wildlife, and local human societies and partially explained by strong snow and sea ice feedbacks implying surface albedo changes. Its strong absorptive ability impacts the Earth radiative budget and contributes to global warming via three main effects: a direct radiative forcing by sunlight absorption in the atmosphere, a modification of cloud properties whose mechanisms remain poorly understood, and a snow and ice forcing when BC is deposited on those surfaces, lowering their albedo and triggering melting (Bond et al, 2013; Hansen and Nazarenko, 2004) This latter effect is of great importance in the Arctic because most of the surface is permanently covered with snow and ice and BC concentrations in snow normally peak in spring, due to the Arctic haze phenomenon (Quinn et al, 2007; Shaw, 1995), when daylight hours increase considerably and mean surface air temperatures rise (Flanner et al, 2007). Given its short atmospheric lifetime from days to weeks, BC impacts can be considerably lowered when mitigation strategies are implemented (Bond et al, 2013)
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